Many useful compositions are made of two components that are not normally mixed together until immediately prior to the time that a quantity of the composition is needed for use. For example, the components of epoxy-based adhesives are stored separately from each other, because once the components come into contact with each other a chemical reaction occurs that eventually turns the mixed composition into a hardened mass. For that reason, epoxy-based adhesives are widely available in packages that include two compartments or separate containers that keep the components of the adhesive initially isolated from each other.
Some packages for multiple-component compositions are relatively large and include a sufficient quantity of the components for multiple applications at different times. For example, epoxy adhesives are commonly available in bulk containers such as cans, jars and squeezable tubes. One component of the adhesive (often called “Part A”) is supplied in one bulk container, and the other component (often called “Part B”) is supplied in another container that typically matches the first container in shape and construction. Such bulk containers are in widespread use because the costs of packaging the components are relatively low.
To prepare an adhesive from the components stored in bulk containers, a quantity of each component is measured, withdrawn from the container and transferred to a mixing location. The mixing location may be a mixing well, a mixing pad or a third container. Next, the user mixes the components, using a spatula, brush or other suitable tool, and then transfers the mixed components to an application site.
However, the practice of supplying multiple-component compositions in two bulk containers is not entirely satisfactory. If, for example, the user does not withdraw the components from the bulk containers in the proper ratio, the characteristics of the resulting composition may be significantly affected. Additionally, the portion of each component that remains in its initial container may be adversely affected over a period of time by exposure to the atmosphere once that container is opened. The user is also compelled to dispose of the mixing pad, well or other mixing container after a single use, or undertake an effort to clean the same in preparation for a subsequent use. Furthermore, care must be taken to ensure that the component from one container is not inadvertently transferred to the bulk container of the other component, where it might contaminate that other component or initiate a chemical reaction that adversely affects the characteristics of that other component.
In recent years, there has been increased interest in “single use” containers for compositions made of two components that are initially kept apart from each other. Such containers typically avoid the need to measure out separate quantities of each component before mixing. These containers also help assure that the components, when mixed, are present in the desired ratio for the desired characteristics of the resulting composition. Additionally, if the components are mixed together within the container, the need for a mixing well, pad, container or other type of mixing structure is avoided.
Compositions made of two or more components that are initially kept separate from each other are widely used in the field of medicine and dentistry, including orthodontia. For instance, many adhesives and cements used in dentistry are made of two components that are not mixed together until immediately prior to use. Examples of two-component dental compositions include RelyX ARC dental cement and F2000 primer/adhesive, both available from 3M Company, St. Paul, Minn. Single use containers for multiple component compositions are especially convenient for storing medical and dental compositions, because the container along with the applicator can be disposed of after use for a single patient. In this manner, the risk of transferring an infectious disease from one patient to another is substantially reduced. Often, only a relatively small quantity of the composition is needed at any one time, and the smaller “single dose” or “single use” containers help ensure that a freshly-mixed batch of the composition is available when needed.